Balloon catheters are medical instruments used in a wide range of fields including percutaneous transluminal angioplasty, percutaneous transluminal coronary angioplasty, and ablation. In general, when a balloon catheter is used for treatment, insertion of the balloon catheter is carried out after protecting the balloon catheter with a tubular protection member called a guiding sheath or the like to allow easy insertion into the body and reduce passage resistance.
In that process, to avoid damaging the balloon by the protection member, the balloon of the balloon catheter is, for example, kept in a thin, deflated state during its insertion into the protection member. As a mechanism for transformation of the balloon, a balloon transformation mechanism having a structure comprising an inner cylinder shaft welded to the balloon tip and an outer cylinder shaft welded to the balloon base end, wherein, by sliding the inner cylinder shaft and the outer cylinder shaft over each other to change the shape of the balloon from an inflatable shape to a thin, deflated shape, insertion and passage of the balloon into the protection member can be facilitated, has been reported (JP 2004-305251 A).
In the balloon transformation mechanism described in JP '251, after the balloon catheter reaches the treatment site, an operation of sliding the inner cylinder shaft needs to be carried out to change the shape of the balloon from the thin, deflated shape to the inflatable shape. However, since the state of the balloon at the tip of a catheter placed in the body cannot be visually observed unless X-ray fluoroscopy or MRI is carried out, there is a possibility that the operation of sliding the inner cylinder shaft is skipped by mistake, followed by the subsequent operation using the balloon having a thin, deflated shape. In such a case, rupture of the balloon might occur due to forced inflation of the balloon having the thin, deflated shape when a liquid is allowed to flow into the balloon in this state, or the treatment might be carried out using the balloon having a shape which is not suitable for the treatment.
In view of this, it could be helpful to provide a balloon catheter having a mechanism that blocks flow of a liquid into the balloon when the balloon has a thin, deflated shape.